Background
Estrogen plays a crucial role in the tumorigenesis of breast cancer (BC), and epigenetic modification by SUMOylation is essential for cancer development. However, the mechanism underlying estrogen’s actions on protein SUMOylation and its effect on BC development are still incompletely understood.
Methods
SUMO1
in BC cell lines was verified via real-time quantitative PCR (RT-qPCR) and western blot. Cell proliferation and colony formation assays was also performed to evaluate SUMOylation as mediated by
SUMO1
. Luciferase activity to examine whether E2 promoted the transcription of
SUMO1
, and chromatin immunoprecipitation (ChIP) assay to determine the binding of estrogen receptor alpha (ERα) to SUMO1 were conduction, and an animal model was used to evaluate the effects of E2-ERα-enhanced
SUMO1
transcription.
Results
E2 promoted
SUMO1
mRNA and protein expression levels in a dose- and time-dependent manner in ER-positive BC cells; it exerted no influence on SUMO2/3 expression; in E2-induced
SUMO1
transcription, ERα, but not ERβ, was essential to the process. In addition, E2-ERα upregulated the transcription of SUMO1 by binding with an estrogen-response element half-site (1/2ERE, in the −134 to −123 bp region) of the
SUMO1
promoter, and E2-ERα induced
SUMO1
transcription-enhanced cellular viability in ER-positive BC cells. To further determine SUMOylation as mediated by
SUMO1
in ER-positive BC, we evaluated novel
SUMO1
target proteins such as Ras and demonstrated that E2 increased Ras SUMOylation and cellular proliferation by affecting downstream signaling-pathway transduction. Finally, our data revealed that E2-ERα enhanced
SUMO1
transcription to promote tumor growth in a BC orthotopic tumor model.
Conclusions
Collectively, our results showed that E2 promoted the transcription and protein expression of
SUMO1
via ERα binding to a 1/2ERE in the
SUMO1
promoter, and that E2-ERα also augmented SUMO1-mediated Ras SUMOylation and mediated cellular responses in ER-positive BC. We therefore achieved significant insights into the mechanism involved in ER-positive BC development and provided a novel target for its treatment.